By Richard Powers

Farrar, Straus and Giroux.

304 pp. $25.

Yet most writers of literary fiction steer clear of science, intimidated by its -ologies and equations, fearful that by refracting human experience through science's prism, they will, as Keats put it, unweave the rainbow.

Not Richard Powers. One of the rare writers who understand that a scientific point of view has the potential to render a fictional world that much richer, Powers was interested in science from childhood. He enrolled at the University of Illinois in 1975 as a physics major, though he soon switched to literature.

In his postcollegiate years, he found himself working as a computer programmer in Boston, before quitting to write his first novel. One MacArthur "genius" grant, one Lannan Literary Award, and one National Book Award later, we have Powers' 10th novel. Like his other books, Generosity explores themes of science and technology - this time, the looming future of genetic engineering - with a mastery that would put any scientist at ease and with Powers' signature feat of remaining simultaneously accessible and cerebral.

Our protagonist is Russell Stone, a professor of creative nonfiction writing at a Chicago art school, an unremarkable man who "has, for most of his existence, dismissed the idea that he might author his own life." On his first day of teaching, Russell is struck by the presence of Thassa Amzwar, a student who appears blissfully, glowingly, impossibly happy. He learns that Thassa is an Algerian refugee, orphaned by war, driven from her homeland - the kinds of experiences that tend to leave their owners in a less-than-euphoric state.

Russell consults the school psychologist, Candace Weld, an attractive single mother with a deep-seated conviction that people are capable of change. Candace diagnoses Thassa with hyperthymia - a persistent state of cheerfulness, high energy, extroversion, and enthusiasm. Word of Thassa's condition leaks to the media and crisscrosses the Internet until it reaches the desk of a scientist named Thomas Kurton.

In Powers' previous novel, The Echo Maker, neurologist and writer Gerald Weber was unmistakably modeled after neurologist and writer Oliver Sacks. Geneticist Kurton shares a remarkable, though not exact, resemblance to inventor Ray Kurzweil. (It's not surprising Powers feels a kinship with Kurzweil. Powers speaks, rather than writes, his novels, dictating them into a computer using speech-recognition technology Kurzweil invented.)

Kurton, like Kurzweil, is a transhumanist: He believes that with science and technology, we can enhance ourselves beyond anything nature alone could have scripted, curing aging and eventually defeating death. All writing is rewriting, Russell tells his students; Kurton wants to rewrite the human race.

Kurton's biotech firm, Truecyte, has identified a network of genes involved in the brain's handling of serotonin and dopamine, the chemical carriers of happiness. Different variants of these genes lead to different set points for overall well-being. Kurton believes that one particular set of variants would constitute a sort of happiness jackpot - and when he hears of Thassa, he sees a chance to confirm his hypothesis. If he's right, he will have discovered the genetic code for happiness, one that can potentially be used to engineer happier generations.

Suddenly, Thassa finds herself in the eye of a growing storm. Kurton wants to study her. Candace and Russell - who become something like foster parents to her, with romance blossoming between them in the process - want to protect her. Tonia Schiff, the host of a Discovery Channel-esque science television show, wants to film her. And Thassa herself just wants to be.

The novel's narrator is not exactly Powers himself, but an Author character, if you will. This little trick of metafiction drives home the true seat of Generosity's drama: the ancient controversy over determinism and free will. "I know what kind of story I'd make from this one, if I could," the Author says. "The kind that, from one word to the next, breaks free." He wishes the book could be "one of those hall-of-mirrors avant-garde novels whose characters try to escape their authors," but his voice serves only to remind us that the characters' fates were determined from page one.

Meanwhile, Russell and Candace decide to write their own book, about someone breaking out of prison. Stories within stories, authors who are characters and characters who are authors - Powers deftly navigates the labyrinthine interplay between determinism and creative control.

If people are ultimately nothing more than their genes, then the project of the novel fails. If the belief that we have the power to make choices is nothing more than a fiction, then fiction itself only amplifies the delusion. "Truth laughs at narrative design," Powers writes. Our desire for narrative - for meaning, for sensible chains of cause and effect - is itself a truth, and in that sense, fiction is a manifestation of everything it is to be human. We think, therefore we crave story. But evolution has sculpted us that way. "The novel will always be a kind of Stockholm syndrome," Powers writes, "love letters to the urge that has abducted us."

Powers has secured a place as one of our most exciting contemporary novelists, contemporary not merely because he is alive and writing (or speaking), but also because he deals with truly modern themes, unafraid to place humanity under science's microscope. He has the guts to use the novel to explore the realities that undermine the very premise of the novel. All that, and it's a relaxing, enjoyable read. Maybe it's in his genes.